There is known a disc drive apparatus which records and reproduces information signals to or from disc-formed recording media, and such disc drive apparatus is equipped with an optical pickup which records and reproduces information signals by irradiating a laser beam onto a disc-formed recording medium through an objective lens.
In recent years, various types of disc-formed recording media differed in recording density and thickness of the cover have been developed, and known examples of such disc-formed recording media include CD (compact disc) based on an operation wavelength of laser beam of 780 nm or around, DVD (digital versatile disc) based on an operation wavelength of 660 nm or around, Blu-ray disc (BD) based on an operation wavelength of 405 nm or around, and AOD (advanced optical disc) based on an operation wavelength of again 405 nm or around. There is also known HD-DVD (high definition DVD) as a standard nearly conforming to the AOD standard, so that AOD in the description below will be understood as including HD-DVD.
As a disc drive apparatus which records and reproduces information signals to or from a plurality of types of disc-formed media differed in the operation wavelength of laser beam, there has been known the one equipped with a plurality of objective lenses corresponded to the individual disc-formed recording media (for example, Japanese Patent Application Publication “KOKAI” No. 2001-110086).
The disc drive apparatus described in Japanese Patent Application Publication “KOKAI” No. 2001-110086 has provided therein a biaxial actuator having a plurality of objective lenses corresponded, for example, to a disc-formed recording medium using a laser beam of approximately 405 nm, and to a disc-formed recording medium using a laser beam of approximately 660 nm, wherein laser beam of approximately 405 nm is condensed by one objective lens onto the recording surface of one disc-formed recording medium, and a laser beam of approximately 660 nm is condensed by the other objective lens onto the recording surface of the other disc-formed recording medium, so as to record and reproduce information signals to and from the individual disc-formed recording media.